Cambior, Golden Star boost reserves at Gross Rosebel — Resource figures climb at La Arena project

Once again, Cambior (CBJ-T) and partner Golden Star Resources (GSC-T) have increased the reserve estimate at their Gross Rosebel gold project in Suriname, South America, by almost one-third.

The Gross Rosebel concession covers 170 sq. km and consists of the North block (containing the Pay Caro, East Pay Caro and Koolhoven deposits) and the South block (containing the Royal Hill, Mayo and Rosebel deposits).

For the six main deposits at Gross Rosebel, proven and probable reserves now stand at 48.6 million tonnes grading 1.6 grams gold per tonne, equivalent to 2.4 million contained ounces of gold using a cutoff grade tuned to a gold price of US$400 per oz. (If a gold price of US$350 per oz. is taken into account, proven and probable reserves decline by 27%.)

The stripping ratio is estimated to be 3-to-1, with 5-metre benches and pit slopes angled at 40 on average.

Within the deposits’ hard-rock and transition portions, reserves are estimated to be 19.5 million tonnes grading 1.9 grams gold at a cutoff grade of 0.7 gram gold.

Within the soft-rock (saprolitic and lateritic) portions are 29.1 million tonnes grading 1.3 grams gold at a cutoff of 0.5 gram.

The updated reserves are based on 1,045 diamond drill holes totalling 108,000 metres, 5,054 auger holes totalling 35,000 metres, and 45 km of trenching.

A revised project budget of $1.3 million has been earmarked for the second half of 1997; about $800,000 was spent on definition drilling this past summer.

Remaining work this year will focus on updating a feasibility study submitted last May to the Surinamese government. This final study is due by the end of the year.

Cambior has already earned half of Golden Star’s interest in Gross Rosebel.

Cambior has spent $16 million on the project; Golden Star, $9 million.

The state mining company Grassalco can acquire a 20% participating interest in the project, at cost, within 60 days of the Surinamese government’s approval of the final feasibility study and the granting of exploitation rights.

Unresolved issues include: an agreement with the Surinamese government and Grassalco on the form and financial structure of the operating company; the ability to secure foreign-investment insurance; the availability of financing, including the structuring of a gold-hedging program; and the relocation of a village currently situated on the concession’s boundary.

Meanwhile, at Cambior’s wholly owned Arena gold project in northwestern Peru, the indicated and inferred resources of the open-pit target have been updated to 19.7 million tonnes of 1.1 grams gold (677,000 in situ ounces), using a cutoff grade tuned to a gold price of US$400 per oz. Silver and copper are also present in grades of 1 gram silver per tonne and less than 0.04% copper.

(At a gold price of US$350 per oz., resources decline by 17%.) Geology on the 16,286-ha mining property consists of sandstones, quartzites and thick, Jurassic-Cretaceous sedimentary sequences intruded by subvolcanic dacite porphyry. Mineralization, which is still open laterally and at depth, occurs both in a copper-gold porphyry and a gold-bearing breccia zone.

The company says the shapes of the mineralized zone and the porphyry system are ill-defined and requires further drilling.

So far, 20 diamond drill holes totalling 4,098 metres have been completed on the porphyry, with the longest intersection consisting of 350 metres grading 0.55% copper and 0.3 gram gold per tonne.

The drilling concentrated on an area at the porphyry contact: a 600-metre section of near-vertical, oxidized breccia made up of sandstone and quartzites, with a width of 70 to 100 metres.

Laboratory tests indicate the mineralization is amenable to heap leaching and that recoveries above 74% are possible.

A further 10,000 metres of exploration drilling are to begin in early 1988, with a prefeasibility study scheduled for the latter half of the year.